code: def test_y():
      """Test the y value"""
      with np.errstate(divide="ignore"):
          x = np.linspace(0.0, 1, 10)
          y = np.true_divide(-1, x + 0.1) + 5
      kl = KneeLocator(x, y, S=1.0, curve_nature="concave")
      assert kl.knee_y == pytest.approx(1.897, 0.03)
      assert kl.all_knees_y[0] == pytest.approx(1.897, 0.03)
      assert kl.norm_knee_y == pytest.approx(0.758, 0.03)
      assert kl.all_norm_knees_y[0] == pytest.approx(0.758, 0.03)
  
      assert kl.elbow_y == pytest.approx(1.897, 0.03)
      assert kl.all_elbows_y[0] == pytest.approx(1.897, 0.03)
      assert kl.norm_elbow_y == pytest.approx(0.758, 0.03)
      assert kl.all_norm_elbows_y[0] == pytest.approx(0.758, 0.03)
  
file_path: yellowbrick/tests/test_utils/test_kneed.py
imports: import pytest
  import matplotlib.pyplot
  import numpy
  from yellowbrick.utils.kneed import KneeLocator
label_desc: Use image node_id 14 for calling a global function with example usage: test_y() without return types